The major aims of the Physical Mapping Section are to construct detailed physical maps of vertebrate chromosomes, to facilitate the sequencing of the corresponding DNA, and to utilize the resulting information for studying important biological problems. We initially focused our attention on the human genome, but are now actively studying myriad other vertebrate genomes. The latter includes a large program of multi-species comparative sequencing being performed in collaboration with the NIH Intramural Sequencing Center (NISC). This involves a series of projects aiming to harness the power of comparative sequencing to address questions in vertebrate genome structure, function, and evolution. The latter work includes major contributions to the ongoing ENCODE project. In parallel, there are other efforts aiming to study regions of the human genome associated with human genetic disease. These efforts have resulted in our identification of the Pendred syndrome gene, a gene responsible for cerebral cavernous malformations, and a gene defective in one form of Charcot-Marie-Tooth syndrome (CMT2D). These findings have opened up numerous new avenues of biological study relating to the structure and function of the genes and their encoded proteins, including the development of mouse models for these genetics disorders. Most recently, we have initiated a number of medical sequencing projects to examine the role of sequence variation in human disease. This also involves collaboration with the NIH Intramural Sequencing Center (NISC), and involve studying diseases such as cystic fibrosis and pseudoxanthoma elasticum.